498 JOHN LINCK ULRICH 



find it difficult to account for the fact that direct progression 

 to the plane occurs in some rats, before it does to the opened 

 door, after the plane is plunged. It would be expected then, 

 that the performance of the plunging of the plane gives "pleas- 

 ure" and not progression to the food. If this is so, then on the 

 other hand, it could not be said to account for the fact that 

 sometimes the reverse takes place and progression occurs, first 

 to the door and not to the plane. Here reward would be as- 

 sumed to fixate direct progression to the food. The effects 

 usually said to be produced by the arousal of pleasure can not 

 be operative in two directions. Moreover, pleasure can not 

 account for the facilitation of both parts of directive integration 

 simultaneously, when the reflex mechanisms of the rat are 

 developed. Much less can a mechanical repetition of a move- 

 ment explain how at different trials progression to or from the 

 plane takes place. 



No problem shows, as does the inclined plane problem, how 

 little reliance can be placed upon repetition in learning. For 

 after 60 trials only a few perfect records are sometimes made, 

 and a repetition of trials does not increase the number of such 

 records. When several consecutive perfect records are made, 

 additional trials ought to produce a continuation of these rec- 

 ords, but as the tables and the learning curve IV show that after 

 a series of perfect records produced much before the sixtieth 

 trial, no additional records of the kind are made, and the results 

 are very poor. Apparently a repetition of trials has no more 

 physiological effect than the taking of food repeatedly has for 

 . / the growth and the development of an organism. More funda- 

 mental considerations are required for the understanding of 

 either learning or of growth. Moreover, the repetition of trials 

 with accompanying sensory excitations have not that predom- 

 inant effect that is attributed to them when it is said that they 

 lead to modifications of the nervous system, such as increasing 

 the permeability of the so-called synapses or, the selecting of 

 neural arcs. Reintegration of the nervous system is not a 

 fundamental consideration in learning, for the inherent inte- 

 grated reflex mechanisms are not improved by learning. In 



